1. Field of the Invention
The present invention relates to an inflator which is mounted in various kinds of vehicles and that is suitable for an air bag to protect a passenger when the vehicle receives an impact. The present invention also relates to an inflator for protecting a passenger when the vehicle receives an impact from a lateral direction of the vehicle, and relates to a method of manufacturing the inflator.
2. Description of Related Art
An inflator for an air bag system for automobile uses, as means for inflating an air bag, a gas generating agent, a liquid fuel and a liquid gas such as a laughing gas. An inflator using carbon dioxide as an inflating means is disclosed in a Fundamentals of a Stored Liquefied Gas Inflator (Bart E. Adams and Mohamed E. Labib, 1999-01-1068). Such an inflator is demanded to function to inflate the air bag, and demanded to be reduced in size and in weight in view of the reducing weight of vehicle itself.
As an inflator for inflating type safety system of an automobile, in order to optimally protect a passenger in accordance with a position of a seat in a vehicle such as a driver side, a passenger side and the like, there are known various inflators such as an inflator for a driver side, an inflator for a passenger side next to the driver, an air bag inflator for a side collision, an inflator for a curtain air bag, an inflator for a knee-bolster air bag, an inflator for an inflatable seat belt, an inflator for a tubular system, and an inflator for pretensioner.
Among these inflators, the inflator for a curtain air bag inflates and develops the air bag instantaneously to make a curtain having a thickness of several centimeters over windows of a vehicle when the vehicle receives an impact in a lateral direction. The curtain air bag is for the sake of protecting a passenger from the impact applied from the lateral direction of the vehicle, and from an impact when the vehicle is rolls over. Therefore, it is necessary to shorten the period to the time when the air bag inflates as compared with a case in which the vehicle receives an impact from the front or the behind. Further, on account of the period of a roll over, the duration of the inflation has to be set to several seconds.
As described above, in the inflator for a curtain air bag, the period of time for the air bag to inflate has to be short and the duration of the inflation has to be long. Therefore, a method of inflating an air bag with a pressurized medium, not with a gas generating agent, is adopted. When a combustion gas of the gas generating agent is used, the air bag can be inflated instantaneously, however, because of a high temperature inside the inflated air bag, the air bag is cooled by a temperature difference with respect to the ambient temperature and is immediately deflated.
On the other hand, when only the pressurized medium is used, a temperature of the pressurized medium is lowered due to release of the temperature of the pressurized medium is lowered, and a temperature in the air bag is also lowered. Therefore, the air bag is heated by a temperature difference with respect to the ambient temperature, and the duration of the inflation can be held for several seconds. However, in case of inflating the air bag only by the pressurized medium, when an environmental temperature is low, there is an adverse possibility such that the inflation is delayed, and it has to be remedied to enhance the reliability as a product. Further, in order to reliably protect a passenger against an impact from the lateral direction of the vehicle, it is also demanded to inflate the air bag in shorter time. Such an inflator for a curtain air bag is mounted to, for example, on a pillar near a rear seat, and it is required to reduce the size as much as possible because a installing place is limited, and it is further required to reduce in weight as well as size in view of reducing the weight of the vehicle itself.
Not only the inflator for a curtain air bag, but also other various inflators are demanded to be small in size and weight from demands of reducing weight of the vehicle itself, and it is demanded to simplify the producing process from demands of reducing the number of parts and producing cost.
As related conventional technique, a device for inflating a flexible container using helium and hydrogen is disclosed in U.S. Pat. No. 5,527,066. A gas flow device for an air bag using a pressurized inert gas is disclosed in U.S. Pat. No. 5,782,486. An air bag apparatus for inflating an air bag by nitrogen or helium is disclosed in U.S. Pat. No. 3,680,886. A side inflator housing for an air bag using a pressurized gas and a gas generating agent is disclosed in U.S. Pat. No. 5,803,493. A pressurized gas inflator using argon or nitrogen as a pressurized gas is disclosed in JP-U No. 3031246.